Supervising device for hydraulic adjusting apparatus in automatic lathes



y 1962 E. HACHENBERG 3,034,300

SUPERVISING DEVICE FOR'HYDRAULIC ADJUSTING APPARATUS IN AUTOMATIC LATHESFiled Oct. 11, 1956 SUPERVHSING DEVICE FQR HYDRAULIC ADJUST- INGAPPARATUS 1N AUTGMATIC LATHES Edmund Hachenherg, Kola, Germany, assignorto Alfred H. Schutte, Kola-Bouts, Germany, a German company Filed Oct.11, 1956, Ser. No. 615,379 Claims priority, application Germany st. 15,1355 Claims. ((11. 60-545) Automatic lathes are known in which thecontrol of the tool slides or other movable parts by any desired camlevers, connecting rods and the like, is eiiected not directly but byway of hydraulic transmission systems. The mechanically-moved parts thenactuate a control piston the movements of which are transmitted throughtwo closed pressure oil columns, acting in opposite directions, to aworking piston connected to a tool holder or a clamping device as thecase may be. It is also known to provide a safeguard against overloadingin the form of a pressure relief valve in such a hydraulic transmissionsys tern.

The object of the present invention is to avoid the difliculties whichmust necessarily arise in the known devices because a certain workingoperation has to be carried out in a specific time while, in addition,it must be ensured that the hydraulically-moved slides, tools orclamping devices have reached the end position reliably determined by astop andremain at such end position for a suiliciently long time. Ifthis is not the case the machine must be stopped, otherwise theworkpieces are not machined accurately or the workpiece is not heldsulficiently fast in the clamping device. However, the pressure in thehydraulic transmission system must not be too high.

According to the present invention, in an automatic lathe of theabovementioned type, the existing difliculties are eliminated in thatthe attainment of the end position of the working piston, at least whenit moves in the direction of application, is controlled by supervisingthe pressure of the pressure oil column which efiects such displacement.One or both of the oppositely acting pressure oil columns is connectedto actuate a compensating piston which, when a specific range ofmovement thereof is exceeded, owing to lack of oil or too high an oilpressure, switches oi the machine and/ or actuates an indicating device.In accordance with an aspect of the invention, in one or both ends ofthe control cylinder in which the control piston moves, there isprovided a spring-loaded compensating piston which takes up a variableposition in accordance with the pressure of the pressure oil and which,in turn, is connected to the control means for switching oil? the driveand/or indicating unallowable pressure oil conditions. The travel ofsuch a compensating piston is limited at the side facing in thedirection of its spring-urged movement by a fixed stop, and the springtension expediently is adjustable. Connected to the compensating pistonby a feeler there is a multiple switch which, when the compensatingpiston is in its specific positions, actuates corresponding indicatingdevices or, in cooperation with a switch operated by a cam rotatingsynchroniously with the control cam, holds closed or opens a holdingcontact arranged in the circuit of the driving motor.

An embodiment of the invention is illustrated in the accompanyingdrawing, wherein the single diagrammatic View shows the application tothe control of a tool slide.

The tool is carried by the tool slide 19 the exact end position of whichis determined by an adjustable stop 11, while the feed and withdrawal ofthe tool slide is effected by a piston 12 which is movable in a workingcylinder 13. The interior of cylinder 13 at the opposite sides of piston12 communicates through pipes 14 and 15 with a am ss Patented May 15,1962 control cylinder 16 at the opposite sides of a control piston 17movable in cylinder 16. The control piston 17 is actuated by a two-armedlever 18, having an adjustable pivot 46, which is, in turn, actuated bya control cam 19 on a shaft 20 also carrying a control cam 21.

The cylinder chambers at the opposite sides of the control piston 17 arebounded inside the cylinder 16 by slidable compensating pistons 22 and23, which are acted upon at the sides remote from piston 17, bycompression springs 24 and 24a respectively and the movements of thecompensating pistons toward the control piston are limited by stops 25and 26, the compression of springs 24 and 24a being adjustable by meansof screws 27 and 28..

The cylinder chambers at the opposite sides of the control piston 17 arefilled automatically through a pipe 29 which communicates with ahigh-level tank 30 receiving oil through a pipe 30m from the circulatorylubricating system of the machine, More oil is always delivered than isnecessary and the surplus flows out of tank. 30 through an overflow 30bfor return to the oil sump. It is not necessary to check the oil levelin the high level tank 30 and to replenish it. As soon as the piston 17,in moving in one or the other direction, has closed the inlet duct 29for the pressure oil, further movement of the piston will compressthecolumn of oil in front of it so that the working piston 12 will move inthe opposite direction. At the same time oil is forced back into thecontrol cylinder 16 from in front of the working piston considered inthe direction of movement of the latter.

The compensating piston 22 is engaged at its side tacing away fromcontrol piston 17 by a feeder 31 connected to a switch '32 which carriestwo contact bridges 33 and 34 arranged in different holding circuits forthe driving motor M of the machine. For example, as shown in thedrawing, the bridge contacts 33 and 34 are connected in series betweenconductors 47 and 48 forming part of a conventional motor controlcircuit that includes the secondary of a transformer 49 having itsprimary energized from supply lines 50 and a relay 51, energized bycompletion of the control circuit to close the motor circuit made up ofconductors 52 and 53 for connecting motor M to supply lines '50.

A switch 35 is actuated by the cam 21 and includes: alternatively closedcontacts 36 and 41. The contact 36 is connected in parallel with thebridge contact 33 of.

switch 32 so that the described motor control circuit can also becompleted when the bridge contact 33 is open and the contacts 34 and 36are simultaneously closed.

The multiple switch 32 further includes bridge contacts 37 and 38 whichare interposed in energizing circuits;

for signal devices 39and 40, and the contact 41 of switch 35 isconnected in series with bridge contact 37 so that the related signal 39is energized only when the contacts 37 and 41 are simultaneously closed.

The bridge contacts 33, 34, 37 and 38 of multiple switch 32 are disposedrelative to the corresponding fixed contacts so that, when thecompensating piston 22 and the feeler 31 are displaced toward the left,as viewed in the drawing, in response to continued movement of piston 17toward the left following engagement of slide 10' with stop 11 undernormal operating conditions, contacts 33 and 34 are simultaneouslyclosed while contacts 37 and- 38 are simultaneously opened (as shown).Further, contacts 33 and '34 are positionally related so that a smallermovement of teeler 31 toward the left, as viewed in the drawing, willcause closing only 'of bridge contact 34,

while contact 33 will remain open. On theother hand,

excessive movement of feeler 31 toward the left, as viewed in thedrawing, will cause opening of both contacts 33 and 34, and simultaneousclosing of contact 38.

The cam 21 is arranged with respect to the cam 19 so that, when theradially enlarged portion of cam 19 is with the contacts 36 and 41intheir open and closed conditions, respectively. On the other hand,when the this way it is possible to adjust the ranges and the positionsof the ranges at which the switching arrangements for the indicatingmeans 39 and All come into operation.

If there is too little oil in the pipe 15 and in the cylinder chambersconnected therewith, the supply can be replenished by operating a handpump 42. In the supply replenishing pipe at non-return valve 43 and ashut-elf valve 44 are arranged in series.

The operation of the above described device is as follows: During apredetermined portion of each revolution of the cam19 in the directionof the arrow 45, it

tion in which the contact bridge 34 is opened but the contact bridge 38is closed. Thus, the control circuit for the motor is interrupted andthe driving motor comes to a stop while the indicating device 40 lightsup.

In the constructional'form described above a tool slide 10 iscontrolled, the working position of the tool being determined by a stop'11; The actuation of a clamping device for the workpiece can beeffected in a similar presses the control piston 17 towards the left andapplies pressure to the pressure oil column in the pipe 15, so that thecolumn advances the working piston 12 with the tool holder 10 so far asto abut the latter against the stop 11. Owing to the pressure of the oilon the left-hand side of the control piston 17, the compensating piston22 is pushed back from the stop 25 in opposition to the action of thespring .24 and the compensating piston presses back the feeler 31 sothat the two contact bridges 33 and 34 are simultaneously closed, while,on the contrary the two contact bridges 37 and 38 are opened. Therefore,the oil control arrangement operates as required,

contact 41 is openeda Even though the pressure in cylinder 16 at theleft hand side of piston 17 is reduced by reason of the return of piston17 toward the right, so that contact 33 is opened, the control circuitfor the driving motor is still completed by way of the contact bridge 34and contact 36. The circuits of the indicating devices 39 and 40 arealso interrupted, since the supply of cur- 'rent to the indicatingdevice 39 is interrupted at the open contact 41, and the supply ofcurrent to the indicating device 40 is interrupted at the open contact38. When unallowable oil pressure conditions occur, the following takesplace:

If there are excessively great oil losses due to leakage in the pipe 15,the compensating piston 22 will no longer be'lifted away from the stop25' or will not be moved away to an adequate extent following engagementofslide 10 with stop 11. The switch 32 is then in a position inposition. On the other hand the bridge contact 33 is situated in the oor open position. Then if the control shaft 20 rotates further and thecontact 36 is opened and the contact 41 is closed, the holding circuitof the driving motor is interrupted at 36 so that the motor is stopped.At the same time, the indicating device 39 is fed with current throughthe contacts 41 and 37 so that it lights up. The quantity of pressureoil which is lacking can be added to the system by operating the hand,pump 42.

If the working piston 12 cannot reach its normal end position, thepressure in the pipe 15 and related part of cylinder 16 increases to avalue higher than normal, since the control piston 17 is forcibly movedthrough its full 7 stroke by the cam 19'. As a result, the compensatingpiston 22 moves further outwards and compresses the spring 24 stillfurther; When the highest permissible pressure" is exceeded in the pipe15, the compensating piston ,22, by means of the feeler 31-, moves theswitch 32 into a posi manner. In that case, movement of the workingpiston is stopped either by the clamping of the workpiece or by a fixedstop in the clamping device.

I claim:

1. In an automatic lathe having a driving motor and electric controlmeans therefor, the combination of an operating cylinder having anoperating piston reciprocable therein through a working and returnstroke to actuate a part of the lathe, a control cylinder, a controlpiston reciprocable in said control cylinder, cam operatedmeans forreciprocating said control piston, conduits connecting said operatingandcontrol cylinders at the opposite sides of the pistons therein, saidcylinders and conduits being filled with hydraulic fluid to define aclosed hydraulic transmis- Sion system for effecting said working andreturn strokes of said operatingpiston in response to movement of saidcontrol piston in one direction and in the opposite direction,respectively, at least the end of said control cylinder toward whichsaid control pistonmoves in said one direction being defined by acompensating piston reciprocably slidable in the control cylinder andsubjected to the pressure in said system at the adjacent side of thecontrol piston, spring means opposing the movement of said compensatingpiston by the pressure in said system, and multiple throw switch meansadapted to be interposed in the electric control means for the drivingmotor and actuated by movement .of said compensating piston to halt theoperation of the motor in response to a shortage of fluid in said systemat the end of said working stroke and in response to the occurrence ofan excessive pressure in said system during the working stroke.-

2. In an automatic lathe, the combination as in claim 1; furthercomprising first and second indicating means controllable by said switchmeans to signal the bait of operation of the motor upon a shortage offluid in Said system at the end of the working stroke and upon theoccurrence of an excessive pressure in the system during a workingstroke, respectively.

3. In an automatic lathe, the combination as in claim 1; furthercomprising a fixed stop limiting the movement of said compensatingpiston in one direction.

4. In anautomatic lathe, the combination as in claim 1; furthercomprising means. for adjusting the force with which said spring meansopposes the movement of said compensating piston by the pressure in saidsystem.

5. In an automatic lathe, the combination as in claim 1; furthercomprising means for positively limiting said'working stroke of saidoperating piston.

6. In an automatic lathe, the combination as in claim 1; furthercomprising normally inoperative pump means for supplying hydraulic fluidto the one of said conduits connected to said control cylinder at theside of said control piston facing in said one direction of movement inthe event of a shortage of fluid in said system. i

7. In an automatic lathe, the combination as in claim 1; wherein saidswitch means includes first and second contacts connected in series tocause operation of the motor when said first and second contacts aresimultaneously closed,'said first and second contacts being arranged toclose simultaneously only in response to a predetermined pressure actingon said compensating piston and to open individually in response topressures on said compensating piston which are respectively less thanand greater than said predetermined pressure; and further comprising acam actuated switch operated synchronously with said cam operated meansand having a normally open contact con nected in parallel with saidfirst contact and closed following said working stroke to prevent a haltin the operation of the motor by reason of a reduced pressure acting onsaid compensating piston during said return stroke.

8. In an automatic lathe, the combination as in claim 7; furthercomprising first indicating means operative to indicate a shortage offluid in said system at the end of the working stroke, second indicatingmeans operative to indicate an excessive pressure in the system duringthe working stroke, and control circuits for said first and secondindicating means, respectively; and wherein said switch means includesthird and fourth contacts which are respectively closed only in responseto pressures acting on said compensating piston which are less than, andmore than, said predetermined pressure, said third contact beinginterposed in said control circuit of the first indicating means foroperating the latter when said third contact is closed, and said camactuated switch further having a normally closed contact connected inserieswith said fourth contact in the control circuit of said secondindicating means, said normally closed contact being opened followingsaid Working stroke so that said control circuit of the secondindicating means can be completed only during said working stroke.

9. An electro-hydraulic control system comprising an operating cylinderhaving an operating piston reciprocable therein through a working strokeand a return stroke, a control cylinder having a control pistonreciprocahle therein, mechanical means for reciprocating said controlpiston, conduits connecting said operating and control cylinders at theopposite sides of the pistons therein, said cylinders and conduits beingfilled with hydraulic fluid to define a closed hydraulic transmissionsystem for effecting said working and return strokes of said operatingpiston in response to movement of said control piston in one directionand in the opposite direction, respectively, at least the end of saidcontrol cylinder toward which said control piston moves in said onedirection being defined by a cornpensating piston reciprocably slidablein the control cylinder and subjected to the pressure in said hydraulictransmission system at the adjacent side of the control piston, springmeans opposing the movement of said compensat- 6 ing piston by thepressure in the hydraulic transmisison system, multiple-throw switchmeans actuated by said compensating piston, and electric control circuitmeans having said switch means interposed therein and being interruptedby the latter in response to a shortage of fluid in said hydraulictransmission system at the end of said working stroke and in response tothe occurrence of an excessive pressure in said system during theworking stroke.

10. An electro-hydraulic control system as in claim 9; wherein saidswitch means includes first and second contacts connected in series insaid electric control circuit means, said first and second contactsclosing simultaneously only in response to a predetermined pressureacting on said compensating piston and opening individually in responseto pressures on said compensating piston which are respectively lessthan and greater than said predetermined pressure; and wherein saidelectric control circuit means further includes second switch meansactuated in synchronism with said mechanical means reciprocating thecontrol piston and having a normally open contact connected in parallelwith said first contact of the first mentioned switch means, saidnormally open contact being closed following said working stroke toprevent interruption of said electric control circuit means by reason ofa reduced pressure acting on said compensating piston during said returnstroke.

References Cited in the file of this patent UNITED STATES PATENTS1,557,330 Reynolds Oct. 13, 1925 2,400,840 Peters May 21, 1946 2,437,821Hughes Mar. 16, 1948 2,557,824 I-Iornfeck June 19, 1951 2,583,825 FeltJan. 29, 1952 2,590,022 Larkin Mar. 18, 1952 2,632,956 Crosby Mar. 31,1953 2,674,232 Mason Apr. 6, 1954 2,756,563 Bohlman et a1 July 31, 19562,766,590 Erwin et a1 Oct. 16, 1956

